The invention generally relates to a method of processing a semiconductor assembly. More particularly, the invention relates to a method of processing a semiconductor layer including cadmium and sulfur.
Thin film solar cells or photovoltaic devices typically include a plurality of semiconductor layers disposed on a transparent substrate, wherein one layer serves as a window layer and a second layer serves as an absorber layer. The window layer allows the penetration of solar radiation to the absorber layer, where the optical energy is converted to usable electrical energy. The window layer further functions to form a heterojunction (p-n junction) in combination with an absorber layer. The window layer desirably is thin enough and has a wide enough bandgap (2.4 eV or more) to transmit most available light through to the absorber layer. Cadmium telluride/cadmium sulfide (CdTe/CdS) and copper indium gallium selenide/cadmium sulfide (CIGS/CdS) heterojunction-based photovoltaic cells are examples of thin film solar cells, where CdS functions as the window layer.
However, thin film photovoltaic devices may suffer reduced performance due to the loss of photons in the window layer and/or poor charge collection at the p-n junction. Thus, it may be desirable to increase the light transmission of the window layer and/or improve the junction performance by improving the quality of the window layer.